Lower plug for cementing wells



March 5, 1940. z A DYER 2,192,400

LOWER PLUG FOR CEMENTING WELLS Filed OCT.. 12, 1938 Patented Mar. 5, 1940 UNITED sTATEs PATENT OFFICE LOWER PLUG FOR CEMENTING WELLS dena, Calif.

Application october 12, 193s, serial No. 234,625

5 Claims.

`This invention is an improvement in a lower cementing plug for use primarily in the cementing off operations in oil Wells.

In cementing olf operations in wells, a charge of liquid cement is forced down the casing to the bottom of the hole and ejected into the area surrounding the lower end of the Well casing. Most operators prefer to isolate the cement charge during its introduction to the point of use by cementing plugs below and above the charge which protect the cement from. being intermingled with mud and waterand also furnish a piston like object by which rotary mud under pressure is used to force the plugs and cement through the casing to the point of use.

This application is a continuation in part of my co-pending application led December 22, 193.7, Serial Number 181,133. In that application I illustrate a lower cementing plug comprising a body member having enlarged fluted end portions, a reduced middle portion, and an annular flexible wiper or washer extending outwardly from the reduced portion. 'I'he body is of integral construction and the annular rubber washer is stretched thereon.

An object of my present invention is to construct a plug of the same general type shown in the previous application of two parts to facilitate the casting of same as well as making it possible to install the rubber washer more easily and with a more positive seal with the body member.

Another object of the invention is to provide a plug of the same general design utilizing only a half of the body member, thus reducing cost.

A further object is to. construct a plug with a novel T form of annular washer to improve the seal of same with the body of the plug for preventing leakage where the washer ts into the plug body.

In the drawing:

Figure 1 represents a cross section of the lower extremity of the point of drilling in an oil well with my novel plug therein.

Figure 2 is a similar view showing the plug resting upon a float valve at the bottom of the well, and the cementing operation in progress.

Figure 3 is a top view of my plug.

Figure 4 is a section of the plug taken on the line 4-4 of Figure 3.

Figure 5 is a similar section of a modied form of plug utilizing a half of the plug shown in Figure 4.

Figure 6 is a section similar to Figure 4 showing a modified form of washer having a T cross section.

The cementing plug I illustrated in Figures 3 and 4 is constructed of a lower part or section II and an upper part or section I2. These parts are externally identical, and differ internally in the following particulars:

The upper part has a threaded extension I3 adapted to screw into a threaded recess I4 in the lower part for coupling the two parts together. Instead of being threaded, the extension I3 and recess I4 may be formed in any suitable way to be united by friction, as by providing annular corrugations instead of threads, or the extension and recess may have unbroken walls if the parts are 'constructed of material having adequate surface tenacity. The lower part has an annular shoulder I at the upper end which cooperates with lower face I6 of the upper part to form an annular recess I'I for receiving annular rubber washer I8.

This washer I8 has an external diameter slightly greater than the external diameter of the parts II and I2. It is preferably of suflcient thickness to result in some compression of same when the parts I I and I2 are brought together.

Externally, the complete plug comprises a roughly cylindrical body with a reduced middle portion 20 frusto-conical in design, and with longitudinal fluid passages 2I communicating with the reduced portion 20 and continuing radially to communicate with a central fluid cavity 22 at each end. A castellated form results in which there are ample longitudinal fluid passages, and seating means 25 in the form of legs or base 26 which occupy only a fraction of the area defined by the cylindrical cross section of its plug. This construction affords a free flow of fluid past the plug at the proper time. Inasmuch as both ends are alike, the plug is reversible that is, may be inserted in the well casing either end up.

In Figure l the plug is descending in the well casing 30 below a charge of liquid cement 3l. The plug body ts loosely in the casing, acting principally as a weighted guide for the Washer I8 which has a snug t against the walls of the casing and seals off the cement from mud or water below. At the top of the charge of cement is a top plug 35, see Figure 2, of suitable design and construction to function as a piston. The top plug is forced downwardly by rotary mud 36 under pressure, pushing the cement before it.

When the assembly of top plug, cement and lower plug reaches the bottom of the Well hole, the lower plug engages a float valve or other casing terminal 31 and comes to rest thereon.

AContinued pressure from above causes the outer edges oi' the washer I8 to collapse downwardly, permitting the liquid cement to pass through the iiuld passage of the lower plug and through the oat valve 31. As the cement is forced below the end 38 of the casing it lls-the cavity 39 at the lower end of the well hole and passes upward'into the area 40 surrounding the casing.

After the cement has hardened, the cementing plugs are drilled out to clear the casing.

The modified form of plug illustrated in Figure comprises a lower partl II identical to the lower part in Figure 4, and a similar washer I8. These are assembled bya cap having a threaded extension 5I similar to extension I3 of Figure 4. As an alternative mode of construction part II and cap 50 may be molded or formed as a single piece with the annular recess therein, and the washer stretched Aover and allowed to snap into place. I also consider it to be an equivalent to use the part I I without cap 50, and vulcanizing or otherwise securing washer I8 to the top of the part I I.

This plug must be inserted in the well in the position shown in Figure 5. It performs the same function as the double ended plug and may be used singly, or in tandem, the base 26 ol' v one plug seating on the upper flat surface 52 of another plug.

In the plug shown in Figure 6 the washer Isa is formed with a T cross section which provides an annular ilange extending downwardly and upwardly from the lannular at portion 'II of the washer. Lower and upper parts IIa and I2a are formed with annular recesses I2 and I3 respectively which receive the ange 10. This Junction between the washer and the plug body improves the seal between washer and plug body l and eliminates any possibility of leakage past the inner edge of the washer which otherwise might occur by distortion oi' the washer when under pressure.

This T form of washer may be used with the plug illustrated in Figure 5. In such case, the lower part should have the recess as found in part IIa, and the cap should have a recess to correspond with the recess in part I2a.

whau claim is:4

1. Acementingplugoithetypedescribedcom- .prislng a pair of cooperating members secured together and forming an approximately cylindrical body having longitudinal fluid passages, and an annular flexible washer seated between the members and having a diameter greater than the diameter oi' the body, the washer being formed with a ilange at the inner edge `thereof and the said members being formed with annular recesses to receive the iiange.

2. A cementing plug of the type described comprising a guide member made in two parts having complementary annular recesses, and a flexible washer secured to the guide member with a. ange tting in the annular recesses.

3. A cementing plug of the type described comprising two members forming an approximately cylindrical body having a central end iluld cavity and longitudinal iluid passages communicating therewith, and an annular iiexible washer seated between the members and having an external diameter greaterv than the diameter of the body, the washer being. formed with a Bange at the inner edge thereof and the said members being formed with annular recesses to receive the iiange.

4. A cementing plug of the type described comprising a member formed in two parts having enlarged uted end portions and a reduced middle portion, there being aligned annular longitudinal recesses at the inner ends of the two parts, and a flexible washer seated between the members and having a T ange iltting in the recesses, the washer having an external diameter greater than the diameter of .the member. I'

5. A cementing plug of the type described com'- prising a guide member having an enlarged castellated end and a reduced portion and an annular longitudinal recess in the .reduced portion, a. iiexible washer seated in the reduced portion and having a ilange iitting in the recess and having any external diameter greater than the diameter of the castellated end, and readily detachable means securing the washer on the guide ZEB A. DYER.

member. 

